Conversion of hydrocarbons



May 18x, 1943 l D. R. cARMoDY CONVERSION 0F HYDnocARBoNs Filed Feb.' 2e.1942 Patented May 18, 1943 coNvERsloN oF HYDRocARBoNs Don R. Carmody,Hammond, Ind., assignor to Standard Oil Company, Chicago, Ill., acorporation of Indiana Application February 28, 1942,. Serial No.432,849 I 7 Claims.

This invention relates to a process for the production of gasoline ofhigh octane number from vnormally gaseous hydrocarbons and pertains moreparticularly to an improved process for the alkylation of isoparainichydrocarbons with selected normally gaseous olenic hydrocarbons.

It is known that isoparailinic hydrocarbons such as isobutane orisopentane can be alkylated by normally gaseous olelns such asisobutylene, normal butene, or propylene in the presence of sulfuricacid as a catalyst. It'has also been dis covered that'under ordinaryalkylating conditions alkylation by ethylene of isobutane or othersimilar hydrocarbons containing a. tertiary car'- bon atom is notcatalyzed by sulfuric acid. It has further been discoveredv that theolenic gases other than ethylene can suitably be converted to thecorresponding alkyl sulfates by absorption in sulfuric acid and thesealkyl sul-,- fates employed for alkylating isoparainic hydrocarbon's inthe presence of sulfuric acid under the usual alkvlating conditions. Incarrying out the .step of absorbing oleflns in sulfuric acid and lthereby eliminating undesirable par'ainic hydrocarbons prior to thealkylation step, a loss is incurred in oleflnic material -due to thecondensation or polymerization of the olens to products of highermolecular weight which are not suitable for use in alkylation and whichcannot be recovered for conversion to gasoline'.

l like products.

' substantially pure oleflnic hydrocarbons under conditions suitable foroptimum conversion of each type of olenic hydrocarbon and blending theresulting alkylate. Another object is to provide an improved process forthe production o1'v aviation gasoline by carrying out an alkylationprocessl in such a manner that'the alkylate is formed under the mostadvantageousconditions for high yield and in sucha manner that'contamination with inert gases is Substantially reduced. Further objectsand advantages will become apparent as the description thereof proceeds.

The attached drawing which forms a part of the specification is a simpleflow diagram illustrating one lpreferred embodiment of my invention. y l

My\process in brief includes the recovery of substantially pure ethylenefrom a refinery C2 stream, the conversion of C4 and/or C3 olen's to thecorresponding alkyl sulfates without substantial formation ofpolymerization or con- 'densation products, -the alkylation of anisoparaiiinic hydrocarbon with the pure vethylene under alkylationconditions suitable therefor" employing a Friedel-Crafts type catalyst,and

alkylation of an isoparainic hydrocarbon with ered from the cracking,thermal or` catalytic, of,

petroleum, or petroleum fractions, andmay have been separated from gasesof higher molecular weight by fractionation, absorption and stripping,

etc. The ethylene gas stream will usually contain ethane as well asvarying quantities of methane and hydrogen depending on the previousmethod of segregating the C3 hydrocarbon cut from higher molecularweight hydrocarbons. Absorber l0 contains concentrated sulfuric acid,preferably of greater concentration 'than 90% H2504 and more desirablyv94% I-lzSO4v or higher, which. enters through line I2 at the upperportion of the absorber I0. The ethylene-containing gas stream entersthe base of absorber Il)` through line I I and the addition of thisethylenecontaining stream is regulated in such a way as to obtainyconcentrated sulfuric acid'eester inf-the l'75 F. to about 100 F. Theunabsorbed gases,

' which will be mainly ethane together with any methane and hydrogenpresent, pass overhead -from absorber' II! through line I3 and can bediscarded'or used for fuel gas and other similar purposes.

The concentrated ethylsulfuric acid is passed into stripping tower Ilfrom absorber I0 via. line I5; and enters at the upper portion thereof.A gas stream containing unsaturated Cijiydrocar-A bons or unsaturatedCrhydrocarbons, or a mixture of the two, with or without thecorresponding paraftins, enters stripper I4 through line I6. Althoughthe unsaturated C3 and/or C4 hydrocarbons can be obtained from anysuitable source, they are generally easily available, in petroleumrenery gas streams particularly from the depropanization ordebutanization o1 cracked gasoline. Various methods are well known forfractionating and recovering normally gaseous hydrocarbons from gasolineand any of these may be employed. I especially prefer a fraction rich inC4 olefins. Another source is from the dehydrogenation of natural gasbutane or propane. The ethylsulfuric acid is added to stripper I4 and asthe gas stream passes countercurrent therethrough the ethylene isliberated and propyl and/or butylsulfuric acid is formed. The ethyleneof the ethylsulfuric acid is displaced by propylene and/or butylene andthe ethylene.

freed without further absorption. At the same time, the polymerizationof the Cs and C4 olens to higher molecularweight hydrocarbons issubstantially precluded. The stripper is so regulated as to`temperature, pressure, and velocity of the -gas stream passingtherethrough that substantially only alkylsulfuric acid passes out thelower part of the stripper, while substantially` the only olefin passingoverhead is ethylene, a1- though the saturated hydrocarbons. which mayhave been -present in the gas stream are thus withdrawn from the system.Stripper I4 is maintained at about 30 F. and at pressures within therange from about 1 to about 100 atmospheres, preferably at about 5 toabout 25 atmospheres pressure.

The butyl sulfuric acid withdrawn from the base of stripper I4 isdirected to sulfuric acid alkylator I'I via line I 8. Suilicient`additional strong sulfuric acid is added to alkylator I1 via line I9and line 20 to maintain the concentration in the alkylaltor betweenabout 90 and 100%, preferably about 95 or 96% H2SO4 based on the watercontent ofithe acid mixture. Isobutane from any suitable source (notshown) is added through line 2I and line 22 and can be mixed with the'alkyl sulfaites in line I8 vprior to alkylator I'I or mixed with thesulfuric -acid from line I9 via line 23 be fore injection into alkylatorI1. Alkylator I'I is maintained at the usual alkylating conditions foundoptimum for a process of this type; for example, at a temperature withinthe range from yabout 20 F. to about 100 F., |but preferably from :aboutF. to about 80 F., and under suilicient pressure to maintain thereactants in the liquid phase. The reactants are fed to the alkylator ata rate of about 0.01 to about 10 volumes of reactant per volume ofstrong sulfuric acid per hour. The feed should contain a mol ratio ofisoparan toolefin absorbed in the acid within the range of from about1:1 to about 10:1 and preferably about 4:1. Any suitable apparatus canbe used which is capable of insuring intimate contact of the reactantsand catalyst, together with means, if necessary; for controlling thetemperature of the reaction. A portion of the emulsion of sulfuric acidalkylate, unreacted hydrocarbons, acid and alkylsuliuric acid isrecycled through lines 24a, 30 and 20 to alkylator I'I and the remainderwithdrawn through line 24 and directed to settler 25 in whichstratification of the acid and hydrocarbon layers occurs. Thehydrocarbons together with unreacted gases are withdrawn overhead vialine 26, neutralized and washed (bv means not shown), if desired. anddirected to fractionator 21 via line 28. The acid from the base ofsettler 25 is withdrawn through line 29 and, if still of alkylatingstrength, can be recycled via line 30 to line 20 and alkylator II. Ifthe acid is substantially spent for alkylation but is not yet below 90H2804 titratable acidity, it can be recycled to the ethylene absorptionstep via line 3l which joins line I 2. If completely spent for eitherpurpose, of course, it can be withdrawn via. line 32. It is to be notedthat usually an acid having a titratable acidity of lessythan 90% HzSO4,or in that region, is comparatively ineffective for promoting thealkylation of isoparailns with olefins or alkylsulfates. Apparently thetitratable acid strengthis determined in a large'part by the amount ofhydrocarbons in the sulfuric acid, and the acidity shown by ordinarytitration is based on the weight of the sample which, of course,includes the hydrocarbons present. The acidity based on the watercontent of the sulfuric acid will still be of the order of 93 to 95% orhigher, howevery `and is therefore eminently suitable for vuse in theabsorption of ethylene. Accordingly, it is an important step in ourprocess that rthe partially or wholly spent acid from alkylation whichstill has a hydrocarbon-free acidity of 90% or greater be recycled tothe ethylene absorption step.

The ethylene from stripper I4, together with any C4 or Cs paraiinichydrocarons originally present in the gas stream from line I6 passesoverhead through line 33 to alkylator 34 in which the ethylene iscontacted with an isoparaiiinic hydrocarbon in the presence of analuminum halidetype catalyst. Although sulfuric acid does not catalyzethe alkylation of an isoparaiiin with ethylene, it has been found thatvery effective alkylation can be obtained if an aluminum halidetypecatalyst such as aluminum chloride or aluminum bromide, or moreadvantageously an aluminum halide-hydrocarbon complex is employed forpromoting the reaction. The aluminum halide can be used as such orsupported on various materials such as clays, pumice, kieselguhr,alumina. etc. It can be introduced in the form of a slurry in an inertsolvent or be present in the form of lumps over which the reactantspass. A particularly desirable type of catalyst is one formed by thereaction of aluminum chloride with a normallyl liquid hydrocarbon in thepresence of a hydrogen halide activator and particularly with aparaihnic hydrocarbon, although aromatic or olefinic hydrocarbons arealso useable. The rcaction product is in the form of an aluminumhalide-hydrocarbon complex, diilicult to analyze, liquid in form, andusually of modiiled activity, i. e., the extreme activity of purealuminum chloride is reduced 'rtoa point where undesirable sidereactions are minimized or eliminated.

Alkylator 34 is maintained at temperatures from about 0 to about 212 F.or higher and at superatmospheric pressures Within the range from about30 pounds per square inch to about 500 pounds per square inch, althoughI prefer that it be maintained within the range from about to about 250pounds per square-inch. A preferred temperature includes the range fromabout 80 F. rto about 150 F. and most desirably from about F. to about135 F. It is desirable to add an activator such as a hydrogen halide,and more particularly hydrogen chloride, to the reaction, usuallyl inamounts of 5% or less based on the' aluminum chloride present, and itcan be as low as 0.5%. Intimate contact between the reactants and thecatalyst is necessary although it has been ethylene is obtained inconcentrated form and found that the reaction can be carried outsuccessfully if the reactants are passed upwardly through a deep pool ofcatalyst.

Activator is added through line 35 and catalyst through lines 36 and 31.An isoparamn such as 5 isobutane is added from line 2| and line 38 andcan be injected directly into the ethylene stream in line 33'or sentdirectly to alkylator 34 via line 39. The hydrocarbon conversionproducts, -together with unconverted hydrocarbons, are with- 10 drawnfrom alkylator 34 through line 40 and sent to settler 4| wherein aseparation .is made between the hydrocarbons and any occluded ordissolved catalyst. A cooling coi1 or other similar temperature-reducingmeans can be inserted in line 40 to precipitate out dissolved aluminumchloride. The separated catalyst is withdrawn from settler 4| via line42 and can be discarded through line 43 but preferably is recycledthrough line 44 to line 31 and alkylator'34 until substan- 20 tiallyspent.

The hydrocarbons together with activator pass overhead from settler 4|through line -45 and through a washing and neutralizing system (notshown) to line 28 leading to fractionator 21. In 25 fractionator 21,which can be any conventional apparatus for the separation ofhydrocarbons of Various boiling ranges, unreacted gases," whichr will bechiey parailnic hydrocarbons from gas stream I6, and excess unreactedisobutane from line2| pass overhead through line 46 and can be discardedthrough line 41 or recycled through line 4B to line 2 I. In the eventthat the off-gases contain considerable amounts of normal butane or thenormal butane tends to build up in the 3:, system, it may be desirableeither to fractionate in such a manner as to eliminate the normal butaneand recycle only the isobutane, or to direct the total off-gases throughan isomerization unit I` wherein the normal .butane is converted toisobutane suitable for use in the alkylation systems. As a furthermodification it is quite Within the scope of this invention to separatethe normal butanes from the isobutanes and to direct only the normalbutanes-to isomerl- 4,; zation system I and thence back to thealkylation system where they join the previously searated isobutanes.

Hydrocarbons heavier than aviation gasoline can be withdrawnfromfractionator 21 -through 50 ling 49. In the event that this fractiondoes not contain too great a quantity of lhydrocarbons of very highmolecular weight, it is quite possible to use these heavy hydrocarbonsas an aviation safety fuel, or it is equally within the scope of thisinvention to withdraw the hydrocarbons of safety fuel boiling range as aside stream (not shown) and discard only thev heavy condensation'product through line 49. A blended gasoline of high octane number,balanced volatility, and good lead response is withdrawn as a sidestream through line 50. In the system described the chief product ofalkylating isobutane, for example, with ethylene in alkylator 34 will bediiso.-

propyl, while the alkylate' from alkylator I1 will 5' be chieflyisooctane, or isoheptanes and isooctanes depending upon the exactoleflns used in the process; The fraction withdrawn through line 50therefore represents a product eminently suitable for use in aviationengines which demand not only high octane number but a fuel having adefinite boiling range and certain volatility characteristics requiredfor ease in starting not possessed by isooctane alone.

My process has the definite advantage that or hydropolymerized withoutconversion.

substantially free of diluents such as ethane, methane, hydrogen, etc.

isopropyl from refinery light gas streams is concentrating the ethylenetherefrom, and my process provides an extremely economical andadvantageous process in that respect. Great difficulty has also beenencountered in concentrating C3 and particularly C4 olens by conversionto the alkyl sulfate in avoiding excess losses due to the conversion ofa part of the olenic feed to polymers and high boiling condensationproducts. By using ethylsulfuric acid as the absorption medium, thepropylene and butylenes are not only converted substantiallyquantitatively to alkyl sulfuric acid, but there is little or notendency for a part of the oleflns to be polymerized Furthermore, thereis no dilution of the sulfuric acid alkylation catalyst due to the useof diluted, low concentration sulfuric acid for olefin absorption, whichis the case under ordinary absorption'conditions used for forming butylsulfates.

identical. Ordinary absorption of mixed oleflns in sulfuric acid eitherrequires a different strength of acid for each particular olefin orvarying pressures if the same strength acid is used throughout. Whenusing ethylsulfuric acid this selectivity appears to be eliminated orreduced to such an extent that the loss of olens is negligible.

Although I have designated the reaction product of ethylene and sulfuricacid as ethylsulfuric acid, and the reaction products of Ca and/or C4Aolefins with ethylsulfuric acid as the corresponding alkylsulfuricacids, for the sake of simplicity, I wish to include any and allproducts formed during either of these kreactions within the scope of myinvention.

My process has been illustrated generally, and many details necessary ordesirable for the operation of a commercial unit have been omitted forthe sake of clarity and simplicity, but these details will readilybe-supplied by one skilled in the art. These details include such itemsas pumps, valves, heat exchangers, washing and" purifying means, etc.,all of Which are well-known and their necessity understood. Although Ihave show n one preferred embodiment of myinvention. it should berealized that this is by way of illustration and not by way oflimitation,v and that I intend to be bound only by the scope of theappended claims.

I claim: v

1. A process for the production of a balanced fuel comprising the stepsincluding contacting at least one oleflnic hydrocarbon having more than2 carbon atoms per molecule with ethylsulfuric acid whereby ethylene isliberated and an alkylsulfuric acid corresponding to said olenichydrocarbon is formed, contacting said liberated ethylene with anisoparafllnic hydrocarbonin the presence of an aluminum halide typecatalyst under alkylation conditions, contacting said alkylsulfuric acidwith an isoparaffinie hydrocarbon in the presence of strong sulfuricacid under alkylation conditions, recover-- ing alkylate from each ofsaid last mentioned contacting steps and blending vsaid recoveredalkylates.

2. A process for the production of a balanced l* y One ofthe gravestproblems in the commercial production of dil The acid strengths in myprocess are much more nearly gaseous hydrocarbons containing butyleneand comprising predominantly oleiins having more than two and less thanfive carbon atoms per molecule whereby ethylene is liberated and alkyl-Y sulfuric acid corresponding to said oleilns is formed, contacting saidliberated ethylene with isobutane under alkylation conditions in thepresence of an aluminum halide catalyst to produce an alkylatepredominating in diisopropyl, contacting said alkylsulfuric acidI withisobutane in the presence of strong sulfuric acid under alkylationconditions to producean alkylate comprising isooctane and recovering abalanced fuel comprising a blend of the diisopropyl and the isooctaneproduced in each of said last-mentioned contacting steps.

3. A process for the production of a balanced aviation fuel comprisingthe steps including forming ethylsulfuric acid from anethylene-containing gas stream and sulfuric acid, contacting saidethylsulfuric acid with a normally gaseous hydrocarbon stream containingolens having more than two carbon atoms per molecule under conditionswhereby said ethylene is liberated from said ethylsulfuric acid andalkylsulfuric acid is formed corresponding to said oleflns in saidnormally gaseous hydrocarbon stream, separating said liberated ethylenefrom said alkylsulfuric acid, contacting said liberated ethylene with anisoparailinic hydrocarbon in the presence of an aluminum halide typecatalyst under alkylation conditions, contacting said alkylsulfuric acidwith an isoparaiiinc hydrocarbon in the presence of strong sulfuric acidunder alkylation conditions, recovering alkylate from each of said lastmentioned contacting steps and blending said recovered alkylates.

4. A process for the production of a balanced aviation fuel comprisingthe steps including forming ethylsulfuric acid from anethylene-containing gas'stream and sulfuric acid, contacting hydrocarbonstream containing olens having more than two carbon atoms per moleculeunder conditions whereby said ethylene is liberated from saidethylsulfuric acid and alkylsulfuric acid is formed corresponding tosaid olens in said normally gaseous hydrocarbon stream, separating saidliberated ethylene from said alkylsulfuric acid, contacting saidliberated ethylene said ethylsulfuric acid with a normally gaseous.

with an isoparaiinic hydrocarbon in the presence of an aluminum halidetype catalyst under alkylation conditions, contacting said alkylsulfuricacid with an isoparalnic hydrocarbon in the presence of strong sulfuricacid under alkylation conditions, recovering alkylate from each of saidlast mentioned contacting steps, returning sulfuric acid from said lastmentioned sulfuric acid contacting step substantially spent foralkyation to said ethylsulfuric acid forming step, and blending saidrecovered alkylates.

5. A process according to claim 3 in which said isoparaflinichydrocarbon is isobutane.

6. A process according to claim 3 in which said olens in said normallygaseous hydrocarbon stream comprise predominantly olefins having fourcarbon atoms per molecule.

'1. A process for the production of a'balanced aviation fuel comprisingthe steps including c'ontacting a light gas stream containing ethylene,ethane and lighter gases with sulfuric acid of greater than H2504content under conditions adapted to form ethylsulfuric acid,`eliminating gases other than ethylene from said contacting step,contacting said ethylsulfuric acid with a C4 stream containing olefinsand paraffns countercurrently underv conditions adapted to liberateethylene and form butylsulfuric acid, recovering said liberated ethyleneand contacting said recovered ethylene with isobutane in the presence ofan aluminum chloride-hydrocarbon complex under conditions adaptedtopromote the alkylation of said isobutane by said ethylene tohydrocarbons having predominantly six carbon atoms per molecule,contacting said butylsulfuric acid with isobutane in the presence ofstrong sulfuric acid under conditions adapted to promote the alkylationof said isobutane by the butyl radical of said butylsulfuric acid,returning sulfuric acid from said last mentioned contacting step to saidethylene-stream contacting step when substantially spent for promotingsaid last mentioned alkylation, recovering alkylatev from said aluminumchloride alkylation step and from said sulfuric acid alkylation step,directing said alkylates to a. common fractionation system, andrecovering from said fractionation system a balanced aviation fuel.

DON R. CARMODY.

